Yes-edumacated guesstimating I would say. From years in marching band, I got a perspective as to what 100 yards and what 10 yards (30 feet) is like. From years doing sound then taping bands I got a different perspective with added guesstimating tools. Also, as someone said, the average depth of a row, foot space with chair, is about 3 feet.
additionally, some measure from stage, I guesstimeasure from stacks. (not always the same measurement)